Load beams of head suspension assemblies are often provided with stiffening structures or other means for providing certain required mechanical properties to such load beams, such as rigidity to the length of the load beam and controlling the resonance frequencies of the load beam. Typically, stiffening rails or flanges are provided at the longitudinal edges of the load beam, such as by bending the edges out of the plane of the load beam. Such edge stiffening rails provide rigidity to the length of the load beam between a substantially resilient spring region at the proximal portion of the load beam (adjacent a portion of the load beam attached to the actuator arm of the disk drive) and the distal tip end of the load beam (which supports the head slider in read/write position to an associated disk). Greater height of the rails generally results in increased rigidity.
Moreover, the height of such edge stiffening rails also affects the resonance frequencies of the load beam. It is important in the design of load beams to design the geometries and features of such load beams so that they either possess resonance frequencies that are sufficiently high so as to be out of the range of vibration frequencies that may be experienced in particular disk drives or the like or to minimize the gain caused by any such resonance frequency. Moreover, as dimensions are reduced within disk drive devices and as head access speeds are increased, it becomes increasingly difficult to provide small enough head suspension assemblies having the requisite mechanical properties.
Another manner of increasing rigidity is to simply form the load beams from thicker materials. However, increased thicknesses also undesirably result in increased spring constants. Increased thicknesses also increase the mass of the load beam which generally has a negative effect on resonance frequencies and slows the response time for disk access. Rails are advantageous in that the mechanical properties of load beams can be controlled without negative effects on the spring constant and with less mass. A disadvantage of side rails, however, is that they add mass as far away from the center line of the load beam as possible which can negatively affect torsional resonance frequencies.
Load beams having side edge rails for increasing rigidity are described, for example, in U.S. Pat. Nos. 3,931,641, 4,734,805, 4,853,811, 4,933,791, 5,003,420, 5,027,240, 5,027,241, 5,079,660, and 5,081,553.
Stiffening structures provided on the surface of the load beam have also been developed. Such load beams are described, for example, in U.S. Pat. Nos. 3,931,641, 4,996,616, 5,131,871, 5,142,424, 5,166,846, and Japanese unexamined published application 1-62877. An advantage of surface stiffening or reinforcing structures spaced from the load beam edges is the ability to control mechanical properties with more ribs at lower heights. Moreover, surface structures permit the added mass to be more centrally located along the center line of the load beam to lessen the negative effects of the greater mass on torsional resonance frequencies. The Aoyagi et al. reference, U.S. Pat. No. 4,996,616, specifically discloses load beams having both surface reinforcement ribs that are spaced from the side edges and bent side edges. The advantage of the Aoyagi et al. design is that the combination of the bent side edges with the reinforcing ribs can be together used to control the mechanical properties for optimized rigidity and resonance frequencies. Again, overall height can be reduced. These advantages, however, may come at the expense of increased production costs in making the surface stiffening structures or ribs, particularly when additional components and/or further processing steps, such as metal reworking, are required.